From 1d044ca035dc22df0d3b39e56f2881071d9118bd Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" Date: Fri, 19 Aug 2022 19:17:29 -0300 Subject: video: hyperv_fb: Avoid taking busy spinlock on panic path The Hyper-V framebuffer code registers a panic notifier in order to try updating its fbdev if the kernel crashed. The notifier callback is straightforward, but it calls the vmbus_sendpacket() routine eventually, and such function takes a spinlock for the ring buffer operations. Panic path runs in atomic context, with local interrupts and preemption disabled, and all secondary CPUs shutdown. That said, taking a spinlock might cause a lockup if a secondary CPU was disabled with such lock taken. Fix it here by checking if the ring buffer spinlock is busy on Hyper-V framebuffer panic notifier; if so, bail-out avoiding the potential lockup scenario. Cc: Andrea Parri (Microsoft) Cc: Dexuan Cui Cc: Haiyang Zhang Cc: "K. Y. Srinivasan" Cc: Michael Kelley Cc: Stephen Hemminger Cc: Tianyu Lan Cc: Wei Liu Tested-by: Fabio A M Martins Signed-off-by: Guilherme G. Piccoli Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20220819221731.480795-10-gpiccoli@igalia.com Signed-off-by: Wei Liu --- include/linux/hyperv.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 3b42264333ef..646f1da9f27e 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1341,6 +1341,8 @@ struct hv_ring_buffer_debug_info { int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info); +bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel); + /* Vmbus interface */ #define vmbus_driver_register(driver) \ __vmbus_driver_register(driver, THIS_MODULE, KBUILD_MODNAME) -- cgit From fce444fa37bef2d3382b7b44e42c6ef65040ec67 Mon Sep 17 00:00:00 2001 From: Olaf Hering Date: Sat, 5 Nov 2022 11:54:01 +0000 Subject: hv: fix comment typo in vmbus_channel/low_latency morev vs. more. Signed-off-by: Olaf Hering Link: https://lore.kernel.org/r/20221105115401.21592-1-olaf@aepfle.de Signed-off-by: Wei Liu --- include/linux/hyperv.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 646f1da9f27e..85f7c5a63aa6 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -969,7 +969,7 @@ struct vmbus_channel { * mechanism improves throughput by: * * A) Making the host more efficient - each time it wakes up, - * potentially it will process morev number of packets. The + * potentially it will process more number of packets. The * monitor latency allows a batch to build up. * B) By deferring the hypercall to signal, we will also minimize * the interrupts. -- cgit